Oil well pump control system



Fim-1015i 0R 54569456 Dec. 14, 194s. A, SMH 2,456,456 /-.f

OIL WELL PUMP CONTROL SYSTEM 2 Sheets-Sheet 1 Dec. 14, 1948. A, SMWH2,456,456

oIL WELL PUMP CONTROL SYSTEM Filed Jan. 4, 194e 2 sheets-sheet 2 Powernvenorl rafon A. SmJrh B5 his momes-@amm Patented Dec. 14, 1948 gaetaOIL WELL iUMP CONTROL SYSTEM Grafton A. Smith, Tulsa, Okla., assigner toShell Development Company, San Francisco, Calif., a corporation ofDelaware Application January 4, 1946, Serial No. 639,117

5 Claims. (Cl. 10S-25) l This invention pertains to a system forrecording and/or controlling the operation of oil well pumps, andrelates more particularly to an automatic system for the control ofelectrically driv-' en pumps in wells producing small quantities offluid.

In many wells, especially during the later stages of their exploitation,the quantity of fluid entering the borehole from the formation is oftenless than that which can be readily handled by the pumping equipment,that is, the volumetric capacity of the pumping equipment installed atthe well is such that a sustained operation thereof results in pumpingthe well off or dry. Under these conditions, it is usual to produce suchwells by intermittent pumping, so that the uid is permitted toaccumulate in the borehole during pump shut-down periods, and isexhausted from the well during alternate pump operation periods.

Such intermittent operation of the well pumping equipment may becontrolled either manually, whereby the pump is started and stopped byhand for each operating period, or automatically, whereby the pump isstarted and stopped at predetermined set intervals by a time-responsivemechanism, such as an electrically or spring driven clock.

The disadvantages of manual pump control methods, involving the hazardsof the human element, are obvious. The dispadyraptages of automatictime-resgphsve ,methQgs/ofontrgl muws. he length `of Qfhapafficulartin'peoddring which a wellusiehgt.

mtlhe m-Qper amount of 011 to,

accumulate thereinJfand the ratiognjhiswtidme periodTo '"tlwat'duringwlch the pump is opweg; ated to el'ect'a complte depletion of the 71511,

A'cli/the time-responsive.punipmcpngfn mechanism oftenrgsultswinxhrpgeiime griods being selectedl whereby the oyer-alleiicienuynQL-lhe Ellllllllmeratiglysgaly lowered.

Thus, a well which'was pumped/daily in two 2 duced 9.12 barrels of oilper day, whereby the pump eniciency was raised to 64.4%.

It is therefore an object of this invention tc provide wellmlgpgnnrstimlielilalie. duration of the gmping and shut-down pgxjgdl be correctl oindications secur,e d a n recorded i n QpelatngSaiiLSystem;J

"/I't is also an object o this invention to provide a wel- Mm: whereinthe opjgtipln 0f. eeingglwa C. alliitgiwmhe @id in the borehole isdllllii- It is another object of this invention to provide a systemwherein each pumping period is started by an automatic time-responsivedevice, and is terminated by an automatic device responsive to wellconditions.

It is another object of this invention to pro-` vide a system whereinthe operation of the pump may be automatically stopped at any time whenabnormal conditions develop in the pumping installation.

These and other objects of this invention will be understood from thefollowing description taken with reference to the attached drawings,wherein:

Fig. 1 is a diagrammatic sketch showing the general arrangement of thecomponent. parts of the present system;

Fig. 2 is a perspective diagrammatic view of the controller and recorderelements of the present system;

Fig. 3 shows an alternative arrangement of the circuit of the controller2U of Fig. 2;

Fig. 4 illustrates a type of circular record chart obtained by means ofthe present system;

Fig. 5 is a three-phase circuit diagram of another embodiment of thecircuit of the present invention;

Fig. 6' is a detail view of a magnetic mercury switch used at 61 in Fig.1.

Referring to the drawings, the presentsystem is described by way ofillustration with regard to an electrically driven reciprocating pump,

although it obviously can be used in installationscomprising pumps ofthe centrifugal or other types.

As shown in Fig. 1, a pump located in a well I is actuated by means of asucker rod stringi,

the uid lifted to the surface being directed to storage through a pipe5. The sucker rod string- 3 is reciprocated in the well by theoscillating motion of the walking beam l, which is driven,"

through a pitman 9, crank ll and reducing mechanism i3, by an electricmotor l5, receiving its power through lines l'l and I9. Although thepresent system is described for simplicity with regard to a. singlephase power supply, it is understood that the following descriptionapplies equally well to three-phase systems.

The operation of the motor I5 is started by the closing of the normallyopen magnetic switch 2|. whose electrical circuit is energized from thelines l1 and I9, connected to the electric power supply, and compriseslines i4 and IB and a hand-operated switch I8, such as a single poleswitch, whereby said circuit may be closed through either or both of twobranch circuits connected thereto in parallel: the time-responsivecontrol circuit 2, and the work-responsive control circuit 20.

The control circuit 2 comprises a normally open switch 23, adapted to beclosed by a timeresponsive device such as an electric or spring drivenclock mechanism 25 of any desired type. For simplicity, this mechanismis shown in Fig. 1 asvcomprisinga rotating wheel or disk 21 providedwith a segment 29 adapted to close the switch 23 by contact therewith.It will be seen that the time at which the switch 23 is closed andopened can be accurately pre-set or controlled by suitably adjusting thespeed of rotation of the disk 21 and the size of the segment 29.

The control circuit 20 comprises any desired number of resistancesconnected in series in one of the lines supplying power to the motor l5,for example, line i9. For purposes of illustration, four such resistorsare shown at 3|, 33, 35 and 31. These resistors are preferably made inthe form of at coils and are placed adjacent to a desired number ofspirally wound bi-metallic strips or coils such as shown at 4| and 43,said lai-metallic elements being electrically insulated from the `strips4| and 43 are attached to a rotatable shaft.

49 passing through the center of said coils. The shaft 49 carries an arm5| adapted to describe an arc upon the rotation of the shaft 49. At-

tached to the arm 5| is a friction belt or string z 53, passing over apulley 55 rotatable about a shaft .or bearing 59. Fixedly carried by thepulley 55 is a magnet 6I adapted to rotate together with the pulleybetween stops 83 and 65. Arranged in the proximity of one of thesestops, for example, stop 63, is a switch 61, such for example asmallmercury switch diagrammatically shown in Fig. 6 and comprising a glassenvelope E2, a body of mercury 64 and a magnetically movable pivotedelement 65, the switch being adapted to open when the magnet 5| restsagainst the stop 63 and pulls the element 6B out of contact with themercury. The switch 61 serves to open or to close that branch of thecircuit of the magnetic switch 2l which forms part of the controller 20.

As shown in Fig. 2, the rotatable shaft 49 may have attached thereto, inaddition to the arm 5l, a second arm 1I carrying a pen 13, whereby themotion of the shaft 49 may be recorded on a strip or disk type chart 15,for purposes to be described hereinbelow, said chart being actuated byan electrically or spring driven clock mechanism 11.

It is understood that instead of being connected to the same shaft 49,the arm v5l and. the.

pen-arm ll may be connected to separate shafts, each responsive to aseparate set of bi-metallic coils and resistors connected in series intothe circuit of the motor l5, as shown in Fig. 3 with regard to pen armIll, shaft |49 and elements |3|-I31, |41 and |43.

With the above organization of the .present system in mind, itsopera-tion is as follows:

The speed of the clock-work mechanism 25 is regulated so as to startpumping periods at desired predetermined time intervals. For example, ifthe pump is capable of depleting the well in three hours, and the wellthen requires another four hours to accumulate sufficient fluid for thenext pumping period, the timing mechanism is adjusted for a timeinterval of seven hours between the starting of two consecutive pumpingperiods. For example, the wheel 21 is adjusted to make one completerevolution in seven hours.

With the hand -operated switch i8 closed, the switch 23 is closed bythe. -timing mechanism, which energizes the circuit of the magneticswitch 2| and closes said switch, thereby starting the motor l5 and thepumping operations.

The switch 61, which may be selected as a normally closed switch, thatis, a switch tending to remain closed unless specifically controlled, isopen at that time, since the magnet 6| rests against the stop 53, in theproximity of said switch, and its magnetic eifect pulls the movableelectrode of the switch away from its xed electrode, or the mercury poolif a mercury switch is used. l

The electric currentactuating the motor l5 passes through theresistances 3|-31, heating said resistances, which transmit the heat tothe adjacent bi-metallic coils 4| and 43. The heating of the coils 4|and 43 causes these coils to develop, in well known manner, a torqueeffect which is applied to the shaft 49, thus rotating said shaft andthe arm 5I, for example, in clockwise direction. The pulley string 53transmits this rotation to the pulley 55, which moves lthe magnet 6|away from the stop 53 towards the running stop 65, thereby permittingthe. switch E1 to close. the stop B5, any further rotation of the arm 5|under the effect of further increases of temperature results merely in aslipping action of the belt 53 on pulley 55, this arrangement therebyserving as a protective clutch.

Since the heating of the coils 4| and 43 proceeds quite rapidly once themotor I5 starts operating, the switch 61 closes very soon thereafter, sothat by the time the branch control circuit 2 opens, for example, afterthe segment 29 has rotated past the switch 23 and has permitted saidswitch to open, the circuit of the magnetic switch 2| remains energizedthrough the branch'of the controller 2D, holding switch 2| closed tocontinue supplying power to the motor 1i When, after a certain period ofpumping, for example after two hours, all the :duid accumulated in thewell has beenexhausted, the pump begins to pump off, that is, the motorI5 contnues to reciprocate the pump in the well at the same rate withoutany appreciable amounts of fluid being lifted to the surface. Since thework done is the product of a force by the distance acted through, or inthe present case, a function of the product of the weight of the Wellfluid by the distance through which this iluid is being lifted, it willbe seen that considerably less energy will be required to operate thepumping equipment After the magnet comes against aaaese when it ispumping off than when it is working at full load. Thus, for example, ifthe pump required 3 1/2 kilowatts for operation at full load, it mayrequire only about 2 kilowatts when pumplng ofi. The amount of currenttaken by the motor |5 being thus greatly reduced, the heating eect ofthe resistors 3 |-3l is likewise decreased below a predetermined minimuman the bi-metallic coils, upon cooling, reverse the torque applied tothe shaft 49, and thus pull the magnet back to the stop 53, opening theswitch 61 and thus stopping the motor i5 by the de-energization of thecircuit of the magnetic switch 2l and the opening of said switch.

The use of the recording device of Fig. 2 in the controlling systemdescribedhereinabove is advantageous for the following reasons.

In setting the time-responsive control circuit 2, it is important toknow the length of time required by the pumping installation to depletethe Well, and the optimum time required by the well to accumulate'therequired amount of oil for the next pumping period. For this purpose,the control circuits 2 and 20 may be removed or rendered inoperative inany desired manner, for example, by closing a switch 8 l, and thepumping operations |80 and |90 controlled by a magnetic switch 2|0similar to switch 2|. The lines |10, |80 and |00 are provided withtransformers |13, |03 and |93, whereby three phase current is suppliedto a control system 200, comprising resistors 23|, 233, and 235 fed bysaid transformers, a bi-metallic' 4coil 243, or a plurality of suchcoils, a rotatable shaft 25| and magnet 25|, similar to these describedwith regard to Fig. l.

It is known that a three phase motor will con-I tinue to run as a singlephase motor infcase of failure in one of the lines supplying thecurrent.

i Such condition is, however, bad as tending to may then be controlledmanually by means of the u switch i8 while recording the performance ofthe pump by meansv of the devices shown of Fig. 2 or 3.

A typical record chart for a period of 24 hours is'shown in Fig. 4. Thischart shows that the pump was started at noon (point A) and operated atfull power for approximately one hour. At B,.

the well became depleted and the pump operated at reduced power for thenext ve hours, raising merely a trickle of oil. The operation of thepumps was therefore manually stopped at C. After leaving the well shutdown for three hours, pumping was resumed and continued for two hours.As shown at D in the diagram, practically no oil was produced during thesecond hour of vthis period. The well was then shut down for four hours,and again pumped for two hours, as shown at E. The production resultsbeing substantially the same as at D, the pumping system was thereafteradjusted for automatic control, pumping being started every four hoursby the controller 2, and being automatically stopped ap- 1proximatelyone hour after the start of each pumping period by the controller 20,the performance of the pumping equipment being checked if desired byrecording diagrams similar to these shown in Fig. 4. In some cases, theoptimum length of the pumping and shut-down period being very accuratelydetermined by the above procedure, it may sometimes be found possible tocontrol thereafter the pumping installation by manual control.

Although the present system has been described for simplicity withregard to a single phase motor, it is understood that it is fullyapplicable to three-phase operation. It is further understood overheatthe motor. With the arrangement shownin Fig. 5, a change in the amountof heat supplied by the resistors 23|-235 to the bi-rnetallic strip 243occurring upon the motor |50 changing from three-phase to one-phaseoperation, causes the magnet 25| to swing toward the switch 267. and toopen said switch, thus operating the magnetic switch 2|0 and stoppingthe motor |50.

The motion of the magnet towards or away from switches El to 251 hasbeen described hereinabove with regard to Figs. l and 5 in a purelyillustrative manner and without limiting in any way the scope of thepresent invention, it being understood that the direction of said motionis determined in every case by the particular type of swit 3h used, suchas a normally open or normally closed switch, the object being in everycase to effect a proper actuation of the circuit controllingr the supplyof power to the pump motor.

it `is further understood that each of the circuits shown in Figs. l and5 is susceptible of use with all the features shown in either figure,but omitted for brevity in the other. such as time controllers,recorders, transformers, switches,

' pulleys, etc.

I claim as my invention:

1. In a well installation comprising a pump for lifting a iiuid tc thesurface, an electric motor to drive said pump, and a power circuit forenergizing said motor, a branch circuit connected to said power circuit,a switch in said branch circuit, time responsive control means rorclosing said switch at predetermined time intervals, a second branchcircuit connected to said power circuit in parallel with said iirstbranch circuit, a switch in said circuit, and control means responsiveto a decrease of the current owing in the power circuit for opening saidsecond switch.

2. In a well installation comprising a pump for lifting a iiuid to thesurface, an electric motor to drive said pump, and a power circuit forenergizing said motor, a branch circuit connected to said power circuit,a switch in said branch circuit, time responsive control means fortemporarily closing said switch at predetermined time intervals, asecond branch circuit connected to said power circuit in parallel withsaid first branch circuit, a switch in said circuit, control meansresponsive to a decrease of the current flowing in the power circuit foropening said second switch, and switch means ln the power circuitadapted to be maintained in a closed position when at least one of saidtwo branch circuit switches is closed, and to be maintained in an openposition when both said branch circuit switches are open.

3.` In a well installation comprising a pump 'for lifting a uid to thesurface, an electric motor to drive said pump, and a power circuit forenergizing said motor, a control circuit connected to said powercircuit, said control circuit comprising a magnetically operable switch,a magnet adapted to move with regard to said switch, thereby closing andopening said switch, a rotatable shaft adapted to move said magnet,bimetallic coil means having one xed end and one end attached to saidshaft, resistor means connected in the motor power circuit, saidresistor means being positioned adjacent to said bilmetallic coil means,whereby the torque exerted by said coil means on said rotatable shaft isvaried in accordance with the heat developed by the current passingthrough said resistors and transmitted to s aid loi-metallic coil means.

4. In a method for intermittently pumping a well producing smallquantities of fluid, the steps of pumping a well throughout a timeperiod longer than that necessary for the pumping equipment to depletethe iiuid in the well, recording the rate of energy consumption by thepumping equipment throughout said period, determining from said recordthe exact length of that effective portion of said period during whichthe fluid was heing pumped fromthe well with a 'high rate of energyconsumption, shutting the well down for an arbitrary period of time,repeating and recording the pumping andrshut-down operations,determining from the record the optimum length of the shut down periodnecessary for the well to accumulate the desired quantity of fluid, andadjusting the well for automatic pumping operation wherein said well isstarted for consecutive pumping operation periods at intervals of timeequal to the sum of an effective pumping period and an optimum shut downperiod.

5. In a method for intermittently pumping a well producing smallquantities of fluid, the steps of pumping a well througl'lout a timeperiod longer than that necessary for the pumping equipment to depletethe fluid in the Well, recording thel rate of energy consumption by thepumping equipment throughout said period, determining from said recordthe exact length of that eiective portion of said period during whichthe uid was being pumped from the well with a high rate of energyconsumption, shutting the well down for an arbitrary period of time,repeating and recording the pumping and shut-down operations,determining from the record the optimum length of the shut down periodnecessary for the well to accumulate the desired quantity of uid, andadjusting the well for automatic pumping operation wherein said well isstarted for consecutive pumping operation periods at intervals of timeequal to the sum of an eiective pumping period and an optimum shut downperiod and is stopped REFERENCES CITED The following references are ofrecord in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,473,441 Perry Nov. 6, 19231,492,844 Hall May 6, 1924 1,892,631 Quigg Dec. 27, 1932 1,896,358Gutrnan Feb. 7, 1933 2,180,400 Coberly Nov. 21, 1939 2,279,958 McKayApr. 14, 1942 2,306,810 Jones Dec. 29, 1942 2,329,614 Holmes Sept. 14,1943 2,334,943 Miller et al. Nov. 23, 1943 2,441,851 Sperow May 18, 1948

